Towards democratization of digital twins: Design principles for transformation into a human-building interface

While legacy building digital twins (DTs), such as building management systems, help building and facility managers to make informed decisions, the real end-users of buildings, i.e., occupants, have been considered as data informants without agency for access to and interaction with DT systems. This is due to the lack of multi-user interfaces for occupants to interact with building systems effectively with sufficient observability and controllability. The research on the design of multi-user interfaces has been limited to specialized services in public, shared spaces, or office-specific experiments and fails to produce detailed design principles. In this study, we explore the "democratization of DTs" as an occupant-building interface that invites occupants to monitor the building-and human-related data and make informed decisions. An occupant participatory approach was employed, consisting of a survey, an experience sampling method, and a co-design workshop, to understand occupants' current experiences with environmental controls and desired methods to interact with a DT system. The findings identified five interaction dimensions between occupants and a novel occupant-in-the-loop DT system that provides occupants with observability and controllability over building systems. Accordingly, we establish design principles for DT systems as an occupant-building interface that supports occupants' dynamic contexts, intuitive controls, collaborative and balanced decision-making between personal comfort and energy consumption, as well as authority and data privacy.